Lead-on-chip (LOC) semiconductor devices have gained widespread acceptance in the semiconductor industry, particularly in the area of semiconductor memories. As illustrated in FIG. 1, an LOC device 10 has leads 14 attached directly above an active surface of a semiconductor die 12 by means of an LOC tape 16. Tape 16 is a solid strip of nonconductive adhesive material whose main purpose is to secure the leads to the die prior to the step of forming the wire bonds 20 which electrically connect the leads 14 to bonding pads 18 on the die surface. In FIG. 1, the bonding pads are shown to be located along the periphery of the die. However, memory devices also include designs having bonding pads along the centerline of the die.
There is a voiding problem with conventional LOC devices. The voids or air bubbles are often formed between the LOC tape and the die surface in the areas between the leads 14 during the attachment of the leads to the die via the LOC tape. As a result of the presence of the voids, moisture absorbed from the ambient collects in these voids which then causes reliability problems for the device. The presence of moisture is detrimental to metallization on the semiconductor die by causing corrosion of the metal lines. Moisture can also cause delamination between the die and the tape when the device is at elevated temperatures, which can affect the integrity of the device.